1. Field of the Invention
The present invention relates to an optical scanning device that forms an electrostatic latent image on an image carrier based on image information, and to an image forming apparatus, such as a copying machine, a printing machine, a facsimile machine, a plotter machine, and a multifunction peripheral (MFP) having a function of at least one of these machines, that include the optical scanning device.
2. Description of the Related Art
Providing, in what is called an in-opposed-directions-scanning scheme in which deflection is performed from a polygon mirror in opposed directions to perform scan in opposed directions by optical scanning systems that are opposed to each other over the polygon mirror, a light-shielding member to prevent such a situation that ghost light reflected from a surface of a lens of one of the optical scanning systems enters the other opposed optical scanning system and adversely affects an image is disclosed in Japanese Patent Application Laid-open No. 2003-202512 and Japanese Patent Application Laid-open No. 2002-196269.
In embodiments in Japanese Patent Application Laid-open No. 2003-202512 and Japanese Patent Application Laid-open No. 2002-196269, a scheme of providing the light-shielding member between incident light on the polygon mirror and scanning light and a scheme of providing the light-shielding member between two incident light beams of the opposed optical systems are described.
The scheme of providing the light-shielding member between incident light on the polygon mirror and scanning light requires that the light-shielding member be arranged in a way that will not cause vignetting of the incident light and the scanning light to occur. Accordingly, the light-shielding member is to be located away from the polygon mirror, disadvantageously allowing a portion of the ghost light to travel to the other opposed optical system. This can result in an adverse effect on an image.
The scheme of providing the light-shielding member between two incident light beams of the opposed optical systems is disadvantageous in that the ghost light is shielded incompletely, allowing a portion of the ghost light to travel to the other opposed optical system.